Production of Nitrous Oxide From Anaerobic Digester Centrate and Its Use as a Co-oxidant of Biogas to Enhance Energy Recovery

Abstract

Coupled Aerobic-anoxic Nitrous Decomposition Operation (CANDO) is a new process for wastewater treatment that removes nitrogen from wastewater and recovers energy from the nitrogen in three steps: (1) NH4(+) oxidation to NO2(-); (2) NO2(-) reduction to N2O gas; and (3) N2O conversion to N2 with energy production. In this work, we optimize Steps 1 and 2 for anaerobic digester centrate, and we evaluate Step 3 for a full-scale biogas-fed internal combustion engine. Using a continuous stirred reactor coupled to a bench-scale sequencing batch reactor, we observed sustained partial oxidation of NH4(+) to NO2(-) and sustained (3 months) partial reduction of NO2(-) to N2O (75-80% conversion, mass basis), with >95% nitrogen removal (Step 2). Alternating pulses of acetate and NO2(-) selected for Comamonas (38%), Ciceribacter (16%), and Clostridium (11%). Some species stored polyhydroxybutyrate (PHB) and coupled oxidation of PHB to reduction of NO2(-) to N2O. Some species also stored phosphorus as polyphosphate granules. Injections of N2O into a biogas-fed engine at flow rates simulating a full-scale system increased power output by 5.7-7.3%. The results underscore the need for more detailed assessment of bioreactor community ecology and justify pilot- and full-scale testing.

Strategien und Potenziale zur Energieoptimierung bei der Wasserwiederverwendung

“…Kommunales Abwasser ist charak terisiert durch 1) einen hohen Anteil von partikulärem CSB, 2) unterschied liche Abbaubarkeiten der gelösten und partikulären CSBFraktionen, 3) schwankende Zulaufkonzentrationen sowie 4) moderate Temperaturen für bio logische Behandlungsprozesse (psychro philer Bereich) (van Lier et al 1997;Seghezzo et al 1998 Gerade bei Standorten, die auf Wass erimporte aus anderen Wassereinzugs gebieten angewiesen sind, kann die Pumpenergie erheblich sein, was das Recycling lokaler Wasserressourcen schnell wirtschaftlich werden lässt. So liegt beispielsweise der Energiebedarf für den Wassertransfer von Nord nach Südkalifornien über einen 700 km langen Aquädukt bei über 2,5 kWh/m³.…”

State-of-the-Art Anaerobic Ammonium Oxidation (Anammox) Technology

“…In this regard, controlling its production and emissions from WWTPs garnered significant attention (Kampschreur et al 2009b). The mechanism of N2O formation through the conventional nitrification-denitrification lies in reducing nitrite-(nitrifier denitrification) and intermediate-formation during the oxidation of hydroxylamine (MH2OH) to NO2 - (Wunderlin et al 2013;Scherson et al 2014). Through this, N2O emission can alleviate up to 14.6% of the nitrogen load (Kampschreur et al 2009b).…”

“…Yet, N2O has also been recognized as a rocket fuel, and thus prompts a concept of N2O generation for energy production from wastewaters, as pursued by Scherson et al (2014). They successfully generated and collected N2O from high ammonium content wastewaters, and used it for co-combustion with methane, achieving about 30% more energy yield in comparison with the combustion with O2 and CH4.…”

Methane and nitrous oxide emissions following anaerobic digestion of sludge in Japanese sewage treatment facilities

“…Additionally, nitrous oxide (N 2 O) has an even higher 100-year global warming potential of 265 (IPCC, 2013), and is released as a by-product of the nitrification and/or denitrification processes. Here again, only very few studies are available on N 2 O emissions following the anaerobic digestion of sludge (Czepiel et al, 1995;Scherson et al, 2014;Toyoda et al, 2011;Tallec et al, 2008).…”